This video will show you what causes this problem and how it can easily be corrected.
Mercury oil tank sensor.
The oil level is full and you replaced the oil level switch but the problem will not go away.
The problem of faulty alarm module is commonly found among the mercury motors.
Low oil sending unit stuck on creating alarm from control panel.
Mercury oil tank level sensor 4 beeps every 2 minutes.
The engine 2 stroke oil tank has a low oil sensor in the bottom of it and can t be replaced without replacing the whole tank.
I also came through same kind of problem few days ago.
Mercury oil tank vent cap mercury mariner 50hp 60hp 75hp 90hp outboard 19299a1 14 99 new mercury marine mercruiser oil tank switch sensor 87 856156t04 87 856156a4.
There are many complaints by the users of mercury motors.